Kf12

Hi HMRC team, My family has set up a mutual fund domiciled in a EU country. My sibling disposed of their shares (for which I am a co-beneficiary) with a realised gain, and transferred the money to a separate account for their own use. Is my sibling the only one liable to declare/pay CGT? Am I liable for CGT since this is a joint investment and I was the co-beneficiary of the shares even though? Thanks.